1. Field of the Invention
The present invention relates, in general, to methods of manufacturing toothbrushes with needle-shaped bristles and toothbrushes manufactured using the methods and, more particularly, to a method of tapering bristles set in a toothbrush and a toothbrush manufactured by the method.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
In conventional methods of manufacturing toothbrushes having tapered bristles, a bundle of bristles, each having an end point from 0.16 to 0.2 mm in diameter, is cut to a predetermined length. Thereafter, the end points of the bristles are hydrolyzed by an alkali chemical or strong acid chemical, thus being tapered. Subsequently, the bristles are washed in water and dried. The bristles are thereafter folded in half and set in holes, formed in a head part of a toothbrush body, using anchors.
However, recently, toothbrushes have followed trends, so that various bristle setting patterns have been required. Furthermore, according to an increase in the size of a bundle of bristles, it has been difficult to fasten bristles with an anchor.
Three methods of manufacturing an anchorless toothbrush are as follows.
First, in a method used by Coronet Co., Ltd. of Germany, bristles are set in a mold and, thereafter, resin is injected into the mold, thus integrating the bristles with a toothbrush body.
Second, in a method used by the Oral-B company of U.S.A, bristles are set in a mold brush plate and, thereafter, the mold brush plate having bristles is placed in a mold. Subsequently, resin is injected into the mold, thus fastening the bristles to a toothbrush body.
Third, the method used by the Boucherie company of Belgium uses a bundle of bristles having a predetermined length, unlike other companies which use a spooled filament as a bristle, and bristles are set in a head insert made of plastic. Thereafter, the head insert is seated into a head insert seat formed in a head part of a toothbrush body. Subsequently, the head insert is bonded to the toothbrush body by ultrasonic waves.
The above-mentioned methods can reliably fasten bristles to a toothbrush body without anchor. However, equipment is very expensive, and productivity is relatively low. Moreover, because a mold, a bristle setting machine and an injection molding machine are integrated together, it is very difficult to change the setting pattern of bristles.
However, toothbrushes manufactured by the above-mentioned methods can realize various bristle setting patterns. Thus, the appearance is superior. As well, the bristle setting pattern can freely be designed to match the tooth structure of every type. Therefore, toothbrushes manufactured by the above-mentioned methods have been popular among consumers.
In the toothbrushes manufactured by the above-mentioned methods, to realize various bristle setting patterns, the volume of a bundle of bristles must become large. As a result, it is impossible to taper bristles using a conventional physical grinding method. It is well known that if bristles are tapered, flexibility is increased so that the gums of a user are protected from injury while brushing the teeth, and penetration ability of the bristles is increased, thus enhancing tooth brushing efficiency.
Due to these reasons, in the case of an anchorless toothbrush, instead of a method of tapering bristles, bristles made of relatively flexible nylon, for example, nylon 6, 10, and nylon 6, 12 are used, thus overcoming the above-mentioned problems. However, a nylon bristle has insufficient durability and water resistance, compared with a polyester bristle. Also, because the penetration ability of bristles, which are not tapered, is poor, tooth brushing efficiency is reduced. Furthermore, bristles made of polyester cannot be used in such a toothbrush due to excessively high stiffness.
Due to these reasons, a tapering process is required even when manufacturing toothbrushes having various setting patterns. There are bristle tapering methods as follow. First, as described above, there is a method 1) in that a bundle of bristles is cut to a predetermined length and, thereafter, the ends of the bristles are hydrolyzed by an alkali chemical or strong acid chemical, thus being tapered. Subsequently, the bristles are washed in water and dried. Thereafter, the dried bristles are folded in half and set in a toothbrush body using anchors. Second, there is a method 2) in that bristles are tapered by a physical method such as a grinding method after a bristle setting process is conducted. Third, there is a method 3) in that bristles are partially tapered by the method 1) and are then additionally machined by the method 2).
The method 2) is problematic in that, because the length of tapered portions of the bristles is relatively short, the bristles are not sufficiently flexible. On the other hand, the method 3) has the advantages of solving the problem of the method 2) and reducing the manufacturing costs. This method was proposed in Korean Patent No. 261658 which was filed by the inventor of the present invention. However, application of this method is limited to a toothbrush to be manufactured using a bundle of bristles cut to a predetermined length. That is, this method cannot be applied to the case using a spooled filament.
In addition, as proposed in Japanese Patent No. 3022762, there is a method in that, after bristles are fastened to a toothbrush body using anchors made of metal, particularly, aluminum, the bristles are immersed in an alkali chemical until just before the cores of the bristles are dissolved, thus tapering ends of the bristles.
However, this method is problematic in that, because the alkali chemical penetrates to the anchors due to a capillary phenomenon during the bristle immersion process, the anchors may be undesirably dissolved. If the anchors are dissolved, the set bristles may be removed from the toothbrush body. Furthermore, in the case of a mass production process, because hydrogen gas is generated when aluminum anchors react with alkali, there is the probability of the explosion of gas due to the heat in a reaction flask. Even if the material of the anchor is changed into brass which has been popular, dissolution may occur because zinc, added to increase the stiffness of brass, reacts with the alkali chemical.
For these reasons, a product manufactured using this method has not been commercialized. In consideration of economical efficiency, only products that are manufactured by the method, in which both ends of a bundle of bristles, cut to a predetermined length, are tapered using a chemical and thereafter folded in half and set in toothbrush bodies using anchors, has been commercialized.
Furthermore, in the case of a toothbrush manufactured by the above-mentioned method of tapering bristles using a chemical after a bristle setting process, each bristle of the toothbrush has a bottle shape, as shown in FIG. 1. Therefore, in the strict sense of word, this bristle cannot be said to be a needle-shaped bristle. Furthermore, this bristle does not have the characteristics of a needle-shaped bristle, including superior penetration ability.
The reason why the bristle is dissolved into the bottle shape, shown in FIG. 1, by a chemical is as follows. In the case that a bundle of bristles is chemically treated, because forty to fifty thousand bristles, which are densely bundled together, serve as a cooling means, the chemical is cooled while penetrating to upper portions of the bristles due to a capillary phenomenon. Therefore, the chemical cannot dissolve the upper portions of the bristles. Conversely, only the ends of the bristles which are immersed in the chemical are dissolved. However, in the case that the bristles, set in the toothbrush body, are chemically treated, because gaps between the set bristles are greater than in the case of the bundled bristles, and because the number of set bristles is less than in the case of the bundled bristles, the set bristles cannot serve as a cooling means. Therefore, the chemical, which penetrates to upper portions of the set bristles due to a capillary phenomenon, is not cooled, so that the upper portions of the bristles are also dissolved by the chemical.
Furthermore, when the bristles, which are partially tapered by the above-mentioned method, are ground by a grinder in the same manner as in method 3), because the bristles, the upper portions of which are dissolved, are inelastic, the thicknesses of the end points of the bristles become uneven. Moreover, a large number of bristles may be bent in a shape shown in FIG. 2 after being ground.
Meanwhile, recently, as proposed in Korean Patent Laid-open Publication No. 2002-0097188, a toothbrush, in which bristles are set in a mountain shape so as to enhance cleaning ability, has been commercialized. However, to dispose bristles in a mountain shape, the bristles must be cut by a cutting machine after the bristle setting process. Furthermore, it is very difficult to taper bristles of such a toothbrush using the above-mentioned conventional tapering method.
Besides, the conventional bristle tapering methods have common problems in which a bristle setting machine, to which an expensive special device is mounted, is required, and a skilled worker is necessary.